Nardia Gray, Nat. Arr. Brit. Pl. 1: 694. 1821.
[as Nardius; named for S. Nardi, an Italian abbot.]
Marie L. Hicks
Plants prostrate, ascending when crowded, forming mats, green to reddish or brownish. Stems thick and fleshy; branching intercalary or terminal; cortical cells thin walled, 32 40 ´ 16 28 µm, sometimes reddish tinged, not distinctly differentiated from slightly longer medullary cells, 35 60 × 16 40 µm; rhizoids scattered along ventral stem in irregular fascicles, some from leaf bases. Leaves succubous oblique, broad, as wide as long or wider, entire, with or without shallowly 2-lobed apex; leaf cells rounded hexagonal with small to large trigones; oil bodies few, large, smooth or granular, opaque or hyaline. Underleaves small, lanceolate, often attached on one side to lateral leaf. Specialized asexual propagation absent. Sexual condition dioicous or monoicous. Androecia terminal, becoming intercalary; bracts similar to leaves, larger, not or slightly modified; antheridia 1 3 per axil, stalks 2 seriate. Gynoecia terminal on main shoots; bracts, inserted on fleshy perigynium, unmodified or shallowly lobed, large in comparison to perianth and concealing it; bracteole present, subulate to lanceolate; perianth short, conical, contracted to crenulate mouth; thickened stem forms a fleshy stem perigynium at base of perianth; calyptra developed atop perigynium; old archegonia situated on calyptra. Sporophyte foot imbedded in base of perigynium; seta 7 8 cells in diameter; capsule globose to ovoid, 4 valved, the walls 2 cells thick; cells of exterior layer large, with nodular thickenings, inner layer smaller with semiannular bands; elaters 150 200 × 8 10 µm, 2 4 spiral. Spores 9 24 µm.
Species 14 (6 in the flora), moist soil or humus: North America, South America (Brazil), Europe, Asia (Java), Africa.
The genus is distinguished by the wide, entire to shallowly 2-lobed leaves, the lanceolate underleaves that are sometimes narrowly connate with lateral leaves on one side. The plants also have unspecialized androecia with bracts scarcely concealing antheridia. Underleaves vary in size and may be vestigial on weak shoots or on proximal portions of stems. They are best developed and should be searched for on apical parts of robust shoots.
Schuster, R. M. 1969. The Hepaticae and Anthocerotae of North America, Vol. 2. New York.